With the advancement of information communication technologies, various wireless communication technologies have recently been developed. Among the wireless communication technologies, a wireless local area network (WLAN) is a technology whereby Internet access is possible in a wireless fashion in homes or businesses or in a region providing a specific service by using a portable terminal such as a personal digital assistant (PDA), a laptop computer, a portable multimedia player (PMP), etc.
The IEEE 802.11n is a technical standard relatively recently introduced to overcome a limited data rate which has been considered as a drawback in the WLAN. The IEEE 802.11n is devised to increase network speed and reliability and to extend an operational distance of a wireless network. More specifically, the IEEE 802.11n supports a high throughput (HT), i.e., a data processing rate of up to above 540 Mbps, and is based on a multiple input and multiple output (MIMO) technique which uses multiple antennas in both a transmitter and a receiver to minimize a transmission error and to optimize a data rate.
Meanwhile, as the propagation of a WLAN is being activated, there appears an environment in which one AP provides service to a large number of non-AP STAs. Furthermore, as mobile devices type non-AP STAs which support a WLAN are increased, there is a need for a method of supporting increased mobility.
An environment in which a plurality of STAs is placed in one WLAN system may include, for example, a Machine to Machine (M2M) network. Unlike the existing WLAN system in which a person accesses an AP through a non-AP STA and receives service, the M2M refers to a network in which a machine supporting WLAN communication becomes the subject and exchanges pieces of information.
The introduction of a WLAN system supporting M2M and an increase in the mobility of an STA may be associated with the operation of an STA based on the battery. For this reason, the power management of an STA may become more important. Accordingly, there is a need for an efficient communication method in terms of the power management of an STA in this WLAN environment.